Digital cameras are primarily designed for use in creating two-dimensional images. In a two-dimensional image, only one perspective is needed. Human vision, however, views scenes from two perspectives, with one perspective provided by each eye of an observer. The parallax that exists between the perspectives is interpreted by the mind of the observer to provide depth information about the scene being viewed. Various electronic and photochemical imaging techniques have been developed that capture images of a scene taken from different perspectives in order to provide three-dimensional (3-D) images. These images are processed and displayed to a user so that one eye of an observer views an image of the scene from one perspective while the other eye of the observer views another image of the scene taken from another perspective. This creates the parallax difference necessary to produce the appearance of depth in the mind of the observer. This is known as “stereoscopic photography” or “3-D photography.”
3-D images can be captured using a digital camera having multiple image sensors, such as the FinePix REAL 3D W1 digital camera available from Fujifilm Corporation of Tokyo, Japan. Such cameras are relatively expensive, however, since they typically require at least two camera lenses, image sensors, and image processors.
To reduce cost, it is known to use a camera that provides a single optical path that is moved along a fixed track, as described in U.S. Pat. No. 5,883,695 to Paul, entitled “Method and Apparatus for Producing Stereoscopic Images with Single Sensor,” and also U.S. Pat. No. 5,325,193 to Pritchard et al., entitled “Single Camera Autostereoscopic Imaging System.” In such systems, different perspectives are captured as the camera is moved to fixed locations along the path.
In all 3-D imaging systems, the apparent depth in the scene is proportional to the extent of the parallax-induced differences between the positions of corresponding features in the presented images. The extent of such parallax-induced position differences is determined in part by the degree of separation between the captured images and in part by the distance from the captured images to the scene. Typically, 3-D imaging systems combine images that are captured at generally the same distance from the scene. This simulates the way that the eyes of a human observer will see a scene. Accordingly, the apparent extent of depth in the resultant output is typically modified by varying the degree of separation between the camera positions for the captured images. This creates an important issue for a photographer in preparing a multi-perspective image: the challenge of selecting the proper combination of camera positions necessary to provide a desired depth effect.
It is desirable to provide the photographer greater control in selecting the extent of separation between camera positions, and therefore the extent of the apparent depth in an image. This control can be provided by allowing the photographer to selectively position the camera to take individual images of the same scene from selected perspectives. These images are later reassembled to form a multi-perspective image. One difficulty in using systems and methods of this type is that it is often difficult for the photographer to know at the time of capture what effect the combination of the images captured at the different camera positions will achieve when they are eventually rendered.
However, in giving the photographer greater control, it is important to provide the photographer with the ability to predict how the resultant multi-perspective image will appear when rendered. Cameras that provide a verification system of individual images captured by a camera do not solve this problem because they are typically adapted to show only one captured image at a time.
It is known to provide a downloadable software application, or “APP” for a smart phone, such as an Apple iPhone that displays previously captured 3-D images using an anaglyphic display method. For example, the “Anaglyph Camera” software application by Nigel Crawley Software enables a user to display two different images of a subject, captured using their iPhone's camera, as an anaglyph image. Anaglyph images are designed to be viewed by a user wearing special 3-D anaglyph glasses having different colored filters for the two eyes (e/g/. a red filter for the left eye and a cyan filter for the right eye). After capturing the images, the user puts on a pair of 3-D anaglyph glasses to view an automatically generated anaglyph, which provides a 3-D effect. The user can then save this 3-D anaglyph image to the photo library on their iPhone, for later viewing. However, this does not enable the user to view a 3-D image during capture, since the glasses are not used until after both images are captured. As a result, it is difficult for the user to capture an image with the desired 3-D effect.
It is known to provide a digital camera using a single image sensor and two separate electronic viewfinders, one for each eye, as described in commonly-assigned U.S. Pat. No. 7,466,336 to Regan et al., entitled “Camera and method for composing multi-perspective images,” which is incorporated herein by reference. A first image is captured, and displayed on one of the electronic viewfinders as a “frozen” image. Next, the user moves the digital camera slightly to compose a second image, which is displayed as a preview image using the other electronic viewfinder. This enables the user to view the 3-D effect as the second image is composed. This approach requires two separate electronic viewfinders, which increases the size and cost of the camera.
There remains a need to provide a compact, low cost, 3-D digital camera that permits a photographer to see a preview or verification representation of a 3-D image during the image composition process.